The present invention relates generally to attachments for power earth moving machines and more particularly to load bearing arrangements for supporting such attachments.
Typical power earth moving machines employ a movable arm of one or more links or members pivotably interconnected and having hydraulic or other actuating devices for operating a tool such as an earth moving bucket or blade supported on that arm. Numerous attachments for the earth moving machine tool have been devised including the fork lift attachment disclosed in my prior U.S. Pat. No. 3,421,642.
In my prior patented arrangement, a fork lift attachment can be easily mounted on and removed from a conventional loader bucket by rotating that bucket in one sense and hookingly engaging the attachment whereupon the bucket is rotated in the opposite sense until the fork lift attachment engages the bucket lower edge thereby locking the attachment to the bucket for subsequent use. This arrangement has met with considerable commercial success due at least in part to the ease with which the attachment may be picked up, used and later removed, freeing the machine for other work. The locking of the attachment to the bucket is not, however, a complete locking but rather the attachment and bucket are coupled firmly only in normal bucket and attachment operating attitudes. Gravitational or inertial forces on the attachment as might be experienced by wildly swinging the arm of the earth moving machine or as might occur when the earth moving machine tool is moved to a position or orientation not suited to normal fork lift operation could allow the attachment to become disengaged from the bucket causing equipment damage or injury to an operator or bystander.
The safety aspects of such a fork lift attachment have been materially improved, for example, as illustrated in my prior U.S. Pat. No. 4,247,243, the features of which may be used in conjunction with the present invention. In this later United States Patent, it will be noted that four hooks are illustrated affixed to the upper edge of the movable bucket, whereas in my earlier U.S. Patent, only three such hooks are illustrated. This additional hook has been used since it was found that the horizontal support bar which interconnects the upper ends of the L-shaped fork lift elements which bears the weight of those elements and associated loads may frequently become bent due to overloading of the fork lift elements. The addition of a fourth hook to the upper edge of the bucket has only partially cured the problem of bending the horizontal support or bar due to overloading.